Cold hardiness & minimum temperature

Is Haworthia cooperi var. truncata (Haworthia cooperi var. truncata)cold hardy? Hardiness zone & min temp

Also called Truncate cooper's haworthia, Window plant truncata.

More about haworthia cooperi var. truncata

About Haworthia cooperi var. truncata

Haworthia cooperi var. truncata · also called Truncate cooper's haworthia, Window plant truncata · houseplant

Haworthia cooperi var. truncata is a small window-leaved succulent forming clusters of plump, blue-green leaves with translucent, flat-topped tips that act as light windows. It stays compact, tolerates lower light than most succulents, and needs gritty soil and careful watering. Slow but easy, and non-toxic to cats and dogs per the ASPCA.

Cold limit: USDA 10-11 (indoor in most US homes) · RHS H1c (15-27°C)

What haworthia cooperi var. truncata's hardiness rating actually means

Haworthia cooperi var. truncata is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Its RHS rating of H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 10-11 (indoor in most US homes) — the zones where it can be left outdoors year-round.

New to these scales? The USDA hardiness zone map explained covers how the zone numbers work, and you can find your own zone with the zone finder.

Minimum temperature — and what happens below it

Minimum survivable temperature is roughly about 5 °C (and never frost). Haworthia cooperi var. truncata has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for haworthia cooperi var. truncata as it gets too cold:

Below about about 5 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches.
A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover.
Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.

Can haworthia cooperi var. truncata go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °C, in shade or dappled light, hardened off gradually.
Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C.
It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

Work back from your local frost dates with the frost-date calculator: the last spring frost and first autumn frost are what really decide when haworthia cooperi var. truncata can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Haworthia cooperi var. truncata hardiness — frequently asked questions

Is haworthia cooperi var. truncata cold hardy?

Haworthia cooperi var. truncata is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Indoor-only in almost every home. Haworthia cooperi var. truncata can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (indoor in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature haworthia cooperi var. truncata can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Haworthia cooperi var. truncata has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is haworthia cooperi var. truncata?

Haworthia cooperi var. truncata is rated USDA 10-11 (indoor in most US homes) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can haworthia cooperi var. truncata survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °C, in shade or dappled light, hardened off gradually. Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C. It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

What happens to haworthia cooperi var. truncata below its minimum temperature?

Below about about 5 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches. A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover. Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.